Important Points
Potentiometer is an ideal voltmeter. Sensitivity of potentiometer is increased by increasing length of potentiometer wire.
If n identical resistances are first connected in series and then in parallel. the ratio of the equivalent resistance.
Rs / Rp = n 2 / 1
If a skeleton cube is made with 12 equal resistance, each having a resistance R, then the net resistance across
1. The diagonal of cube = 5 / 6 R 2. The diagonal of a face = 3 / 4 R 3. along a side = 7 / 12 R
If a resistance wire is stretched to a greater length, keeping volume constant, then
R ∝ l 2 ⇒ R1 / R2 =( l1 / l2) 2 and R ∝ 1 / r 4 ⇒ R1 / R2 =( r2 / r1) 4
where l is the length of wire and r is the radius of cross-section area of wire.
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